Make sure TaskManager does not accept task deployments when shutting down
[FLINK-1205] Fix library cache manager to track references to tasks and revent accidental duplicate registration/deregistration
[FLINK-1203] Use forked execution in all tests, except in the end-to-end integration tests in flink-tests
[FLINK-1198] Broadcast variables are shared between tasks in the same TaskManager
[FLINK-1198] Make Broadcast variables shared per taskmanager, rather than a shared singleton per JVM
             (supports multiple TaskManagers in the same JVM)
[FLINK-1198] Broadcast variables can share initialization via broadcast variable initializers